A light emitting diode (LED) refers to a device utilizing a phenomenon in which minority carriers (electrons or holes) injected by means of a p-n junction structure of a semiconductor are produced and light is emitted due to recombination of the carriers. LEDs include a red LED using GaAsP or the like, a green LED using GaP or the like, a blue LED using an InGaN/AlGaN double hetero structure, and the like.
The LED has characteristics of low power consumption, a long lifespan, installation in a narrow space, and strong resistance against vibration. In recent years, white LEDs in addition to single color LEDs, e.g., red, blue or green LEDs, have been appeared. As the white LEDs are applied to products for automobiles and illumination, it is expected that their demands will be rapidly increased.
In LED technology, methods of implementing white are roughly classified into two types. The first one is that red, blue and green LED chips are arranged to be adjacent to one another, and colors of light emitted from the respective devices are mixed to implement white. However, since the respective LED chips have different thermal or temporal characteristics, there are problems in that a uniformly mixed color cannot be implemented due to changes in a color tone according to usage environment, particularly, the occurrence of color spots, or the like.
The second one is that a fluorescent substance is disposed on an LED chip and the color of a portion of first light emitted from the LED chip and the color of second light of which the wavelength is converted by the fluorescent substance are mixed, thereby implementing white. For example, to an LED chip for emitting blue light is attached a fluorescent substance that emits yellowish green or yellow using a portion of the light of the LED chip as an excitation source, so that white can be obtained by means of mixture of the blue light emitted from the LED chip and the yellowish green or yellow light emitted from the fluorescent substance.
FIG. 1 is a schematic view showing a conventional light emitting apparatus.
Referring to this figure, the light emitting apparatus comprises a substrate 5, a plurality of LED chips 1 mounted on the substrate 5, and electrodes 3 and 4 formed to correspond to the LED chips 1. The light emitting apparatus further comprises an upper package 6 formed on the substrate 5 to surround the substrate, and a molding member 7 formed in a hole at the center of the upper package 6 to encapsulate the LED chips 1.
If the LED chips 1 shown in this figure are red, green and blue LED chips, seven colors can be implemented upon application of a current to the LED chips. In general, such a light emitting apparatus is referred to as a seven-color light emitting apparatus. FIG. 2 is a sectional view showing a section taken along line I-I′ in a case where the conventional light emitting apparatus employs such three-color light emission and the molding member 7 for encapsulating the LED chips 1 is generally formed of a transparent epoxy resin. In the conventional light emitting apparatus constructed of the red, green and blue LEDs, a variety of colors can be implemented by means of selective electrical connection, and white can also be implemented by means of combination of red, green and blue by simultaneously applying a current to all the electrodes. However, since it is generally hard to achieve an optimal condition for mixture of three colors of light depending on the positions of the chips in view of the configuration of a package, it is difficult to implement perfect white light. Since a color variation is generated due to differences in the light among the LED chips, it is difficult to implement a clear white color of light in a small package. Further, since the respective LED chips have different thermal or temporal characteristics, there are disadvantages in that a uniformly mixed color cannot be implemented due to changes in a color tone according to usage environment, particularly, the occurrence of color spots, or the like, and in that luminance is not high. Thus, since the luminance of white light is considerably low in the seven-color light emitting apparatus, it is not frequently used for emission of white light. Such seven-color light emitting apparatuses are used for indicators and decoration not only in mobile phones but also in general electronic appliances. However, in order to implement white light, it is necessary to additionally provide a white LED capable of implementing a flash function of white light using a blue LED and a fluorescent substance.
In the light emitting apparatus shown in FIG. 1, the respective LED chips 1 described above are constructed of blue LED chips and formed to have a fluorescent substance on the LED chips 1, thereby implementing white light. Such a method of implementing white light using blue LED chips and a fluorescent substance has been popularized at present, and the brightness of the white light is influenced by the number of blue LED chips to be used. FIG. 3 is a sectional view showing a section taken along line I-I′ in a case where the conventional light emitting apparatus employs these blue LED chips and a fluorescent substance and the molding member 7 for encapsulating the LED chips 1 is formed of a mixture of a fluorescent substance 8 and an epoxy resin. Accordingly, blue light emitted from the LED chips 1 and light of which the wavelength is converted by the fluorescent substance 8 are mixed, thereby implementing white. Such white LEDs are used for flashes of mobile phones, LCD light sources, and the like.
As described above, in a case where such a seven-color light emitting apparatus is applied to mobile phones and general electronic appliances, it is difficult to implement white light. Since its luminance is very low, an additional white LED for implementing a flash function should be used. Further, since a transparent epoxy resin is generally used as the material of the molding member in case of the seven-color light emitting apparatus, and a mixture of an epoxy resin and a fluorescent substance is generally used as the material of the molding member in case of the white LED using blue LED chips and a fluorescent substance, respective LED packages are separately manufactured and configured due to differences in their configurations and materials.
However, such prior arts have disadvantages in that there is troublesomeness in a process of manufacturing an additional white LED, and respective LED packages are separately manufactured and configured, resulting in an increased exterior size of an apparatus. Accordingly, there is a need for a package integration design and manufacturing technique considering the number of chips, difference in materials, and a circuit configuration.